A heating element of this type on the injector serves the purpose of raising the fuel temperature, with the result that fuel can be injected into a combustion chamber of the internal combustion engine in a gaseous state. This results in improved mixing of the evaporated fuel with oxygen in the combustion chamber. In addition, condensation of the mixture on combustion chamber walls is prevented and the formation of soot particles is minimized.
A heatable injector of the type mentioned at the outset which is used in a compression-ignition internal combustion engine is known from DE 100 45 753 A1, which is incorporated by reference in its entirety. Here, the injector has a heating device which is arranged inside the injector housing in a region in front of the fuel discharge opening for heating fuel which is situated in the fuel space. Here, the heating element of the heating device makes direct contact with the fuel. The heating device has, for example, an annularly arranged resistance heating element; however, semiconductor heating elements or inductive heating elements can also be provided. The heating device is capable of heating the fuel which is situated in the fuel space, with the result that said fuel has a defined temperature before the opening of the fuel discharge opening by transferring the injector needle into its open position and the subsequent injection of the fuel into the combustion chamber of the internal combustion engine. Said defined temperature can be approximately from 100° C. to 400° C. A temperature sensor is provided in the fuel space. Said temperature sensor serves to regulate the temperature of the injected fuel by means of a control and regulating device.
DE 196 29 589 A1, which is incorporated by reference in its entirety, describes a heatable injector for fuel injection in an internal combustion engine. In said heatable injector, a magnet coil is provided for adjusting an injector needle which serves to open and close a fuel discharge opening of the injector. Here, the thermal power loss which is produced in any case by the magnet coil is utilized to preheat the fuel. Furthermore, the injector has a heating coil for additionally heating the fuel which flows through the fuel discharge opening.
EP 2 100 028 B1, which is incorporated by reference in its entirety, describes a heatable injector for fuel injection in an internal combustion engine, in which heatable injector an inductively heatable heating element is integrated into a fuel space of the injector, which heating element is configured as a track which is folded in a zigzag shape between an injector housing and an injector needle and forms a hollow cylinder which extends in the axial direction. As a result, a great heat transfer area can be realized between the heating element and the fuel.
EP 2 385 240 A1, which is incorporated by reference in its entirety, has disclosed a heatable injector for fuel injection in an internal combustion engine, in which heatable injector a heating device is used with a heating element which is composed of a thick-film material. Said thick-film material is applied to the outer side of an injector housing, with the result that, during heating of the heating element, heat is dissipated from the injector housing to the fuel which is situated in a fuel space between the injector housing and an injector needle.
GB 2 206 378 A, which is incorporated by reference in its entirety, has disclosed a heatable injector for fuel injection of an internal combustion engine, in which heatable injector a heating device and a thermocouple are arranged in the interior of the injector.